Regular expressions containing '$' are not processed correctly in Link URL templates

'$' matches the start of a string in both stevesoft and java Regex. If it is used in a regex validator for a token in one of the customisable links menu entries, odd things happen:
0. Try this link for a PDB crossreference:
name: PDB
template: https://www.ebi.ac.uk/thornton-srv/databases/cgi-bin/MACiE/index.pl?query_pdb=1&pdb=$DB_ACCESSION=/$\d[A-Za-z0-9]{3}/=$

1. In 2.10.1, the regex doesn't match. It is stored and recovered faithfully to properties.

2. In the development version of 2.10.2 (with JAL-2316 merged), the regex matches, but it isn't stored and recovered faithfully to the Links preferences - and is corrupted when Jalview is started again.